1. Field of the Invention
The invention relates generally to electrical apparatus, and more particularly to high-current sliding contact assemblies.
2. Description of the Prior Art
Many devices used in the transmission and distribution of electrical energy require sliding contact current transfer members. Such devices include gas insulated or air type disconnect switches, grounding switches, high-current bus switches, and gas insulated transmission bus joints. Each of these devices includes two members relatively movable between an open position wherein the members are physically separated and a closed position wherein the members are in mechanical engagement, allowing electrical energy to flow therebetween.
The problem to be solved in all of these devices is that of reducing electrical resistance at the point of mechanical engagement. This resistance produces a joule heating effect as current passes therethrough, thereby limiting the maximum amount of current which can be safely transferred. Methods for reducing this resistance include providing a large number of separate points of engagement between the separable members and providing contact pressure urging the two members together. While increasing the contact pressure and increasing the number of points of engagement between the separable members reduces the resistance, it also means that the mechanism for moving the members between the open and closed positions must generate considerable force, thereby increasing the cost of the mechanism.
Prior art devices have included a plurality of spring-loaded contact fingers to provide a multiplicity of contact points upon each of which is exerted a spring force in a direction perpendiculr to the direction of relative movement between the separable members. While the contact resistance and therefore the temperature rise was within tolerable limits in such prior art devices, the resulting force required for actuation of the contacts required a costly high-energy actuating mechanism or was otherwise objectionable from a cost standpoint.
It is therefore desirable to provide a contact assembly exhibiting minimum contact resistance at a lower cost.